1. Technical Field
The present invention relates to a variable-wavelength interference filter, an optical filter device, an optical module, and an electronic apparatus.
2. Related Art
According to the related art, a variable-wavelength interference filter is known in which a pair of reflection layers facing each other is provided and the distance between the reflection layers is changed to extract light with a predetermined wavelength from measuring target light (see, for example, JP-A-7-243963).
The variable-wavelength interference filter (optical cavity) described in JP-A-7-243963 includes a first substrate and a second substrate facing each other, high reflection layers arranged on the respective substrates and facing each other via an inter-layer gap, and electrodes arranged on the respective substrates and facing each other. In such a variable-wavelength interference filter, by applying a voltage between the electrodes and thus deforming the second substrate and adjusting the inter-layer gap, the wavelength of light extracted by the variable-wavelength interference filter can be changed.
Meanwhile, in the variable-wavelength interference filter described in JP-A-7-243963, by applying a voltage between the electrodes, the second substrate is flexed and driven in a direction which narrows the inter-layer gap. Therefore, when the inter-layer gap is narrowed in order to extract light on the short-wavelength side, there is a problem that the half-value width of light transmitted through the variable-wavelength interference filter increases (resolution decreases) as the inter-layer gap is narrowed because of the flexure and gradient of the second substrate.